constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The first constellati ...
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...
that is Latinized from φ Aquarii, and abbreviated Phi Aqr or φ Aqr. This system is visible to the naked eye as a point of light with a combined apparent visual magnitude of +4.223.
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...
measurements indicate its distance from Earth is approximately . It is drifting further away with a radial velocity of +2.5 km/s. The system is positioned 1.05 degrees south of the
ecliptic
The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making.
Fr ...
stellar classification
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction gratin ...
of M1.5 III. At an estimated age of 11 billion years, it has exhausted the supply of hydrogen at its core and evolved away from the
main sequence
In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...
. The star has the same mass as the Sun, but has expanded to 35 times the Sun's girth. It is radiating 208 times the luminosity of the Sun from its enlarged photosphere at an
effective temperature
The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...
of 3,715 K, giving it the reddish hue of an M-type star.
On 6 September 2019, it had a close conjunction (geocentric separation <1') with
Neptune
Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...